Waterfall method and apparatus for a data storage device read system

ABSTRACT

A waterfall manufacturing process and apparatus are described for a data storage device. In an aspect, a determination is made during manufacturing of a magnetic storage medium reader system whether a first reader system provides less than a predetermined performance or is nonfunctioning. The reader system includes at least the first reader system and a second reader system with reader elements on the same head. When the first reader system is determined to provide less than the predetermined performance or is nonfunctioning, the reader system is reconfigured during the manufacturing to utilize the second reader system, but not utilize the first reader system, to read the magnetic storage medium. Alternatively, the reader system is reconfigured during manufacturing to read the magnetic storage medium at less than the predetermined performance, or the reader system is situated with a different data storage device configured to function with less than the predetermined performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional U.S. Patent ApplicationSer. No. 62/006,644, filed on Jun. 2, 2014, which is herein incorporatedby reference in its entirety. The subject matter of the presentapplication is also related to U.S. patent application Ser. No.14/644,730, filed on Mar. 20, 2015, which is incorporated by referencein its entirety as if stated herein.

BACKGROUND

Magnetic storage systems are utilized in a wide variety of devices inboth stationary and mobile computing environments. Magnetic storagesystems include hard disk drives (HDD), and solid state hybrid drives(SSHD) that combine features of a solid-state drive (SSD) and a harddisk drive (HDD). Examples of devices that incorporate magnetic storagesystems include desktop computers, portable notebook computers, portablehard disk drives, servers, network attached storage, digital versatiledisc (DVD) players, high definition television receivers, vehiclecontrol systems, cellular or mobile telephones, television set topboxes, digital cameras, digital video cameras, video game consoles, andportable media players.

There is an ongoing effort within the magnetic storage system industryto increase storage capacity while maintaining the same external driveform factor. Track density has increased, and track pitch has decreased,such that magnetic read heads may detect more inter-track noise.Two-dimensional magnetic recording (TDMR) uses multiple read heads toread a single data track, and can improve the reading performance of amagnetic storage system with a high-density disk, as compared to asystem using a single read head.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages describedherein will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a top plan view of a disk drive data storage system in whichembodiments are useful;

FIG. 2 is a top plan view of a data storage disk, showing servo tracksand servo sectors;

FIG. 3 is a top plan view of a hard disk drive (HDD) including a headand a disk including servo tracks, servo sectors, and control circuitryoperable to actuate the head over the disk, in an embodiment;

FIG. 4 is a flow diagram illustrating a waterfall method for a datastorage system, in an embodiment;

FIG. 5 is a flow diagram illustrating an alternative waterfall methodfor a data storage system, in an embodiment; and

FIG. 6 is a sectional view representation illustrating components of asystem that executes methods of an embodiment.

DETAILED DESCRIPTION

In the following description, numerous specific details are disclosed toprovide a thorough understanding of embodiments of the method, systemand apparatus. One skilled in the relevant art will recognize, however,that embodiments of the method, system and apparatus described hereinmay be practiced without one or more of the specific details, or withother electronic devices, methods, components, and materials, and thatvarious changes and modifications can be made while remaining within thescope of the appended claims. In other instances, well-known electronicdevices, components, structures, materials, operations, methods, processsteps and the like may not be shown or described in detail to avoidobscuring aspects of the embodiments. Embodiments of the apparatus,method and system are described herein with reference to figures.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, electronic device, method or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in one embodiment,” “in anembodiment,” and similar language throughout this specification mayrefer to separate embodiments or may all refer to the same embodiment.Furthermore, the described features, structures, methods, electronicdevices, or characteristics may be combined in any suitable manner inone or more embodiments.

Magnetic storage system performance demands and design needs haveintensified. The current demand for larger capacity in a smallerdimension is linked to the demand for ever increasing storage trackdensity. As the density of data on a magnetic storage medium increases,the strength of the magnetic fields generally decrease, in order tominimize interference. With an increase in track density and decrease intrack pitch, magnetic read heads may detect more inter-track noise.Two-dimensional magnetic recording (TDMR) can improve the readingperformance of a magnetic storage system with a high-density disk, ascompared to a system using a single read head. TDMR read headscounteract extraneous noise by using multiple read elements to read asingle data track, and as such, help to create a better signal to noiseratio (SNR) during read back. Additionally, using TDMR, two or moretracks may be detected simultaneously.

However, with a conventional TDMR system with multiple read elements, ora single reader system, an entire media surface may be lost when areader element is nonfunctioning. During the manufacturing stage of aTDMR system, a reader system may be tested, and the system testing mayshow that the reader system provides less than a predeterminedperformance or has failed. A waterfall model may be used to manufacturea TDMR system. A waterfall model is a sequential process, used inproduct development, in which progress is seen as flowing steadilydownward, like a waterfall, through various product development phases.

A waterfall method, process, and an apparatus are described herein for adata storage device read system. In an embodiment, the waterfall methodand process are employed during the manufacture of a magnetic recordingdevice with a TDMR system. As one example, when a single reader elementis determined during manufacturing to provide less than a predeterminedperformance or is nonfunctioning, control circuitry is reconfigured, andthe remaining reader elements on the same head are utilized tomanufacture a fully functioning magnetic recording device.

The determination of whether a reader element or reader system providesless than a predetermined performance or failed may be made duringvarious stages in the manufacturing process, including during head stacktesting.

In another embodiment, when the first reader system is determined toprovide less than the predetermined performance, the first reader systemis retained, and the magnetic storage medium reader system isreconfigured to read the magnetic storage medium at less than thepredetermined performance. In yet another embodiment, the magneticstorage medium reader system is situated with an alternative datastorage device, and configured to function with less than thepredetermined performance.

In an embodiment, the methods and apparatus are utilized with a TDMRhead. A conventional TDMR drive system selects specific reader elementsfor normal operation as a function of armature skew angle, servoperformance, etc. Reader element selection may also be based onformat/error correction capability as determined during drivemanufacturing. These functions may be utilized in part by someembodiments described herein.

The apparatus, system and methods disclosed may be utilized, in anembodiment, with disk drive memory systems, and other memory systemsutilizing a magnetic reading device, including a HDD and a SSHD.

Referring to the figures wherein identical reference numerals denote thesame elements throughout the various views, FIG. 1 illustrates a diskdrive storage system 10, in which embodiments are useful. Features ofthe discussion and claims are not limited to this particular design,which is shown only for purposes of the example.

Disk drive 10 includes one or more data storage disks 14 ofcomputer-readable data storage media. Typically, both of the majorsurfaces of each data storage disk 14 include a plurality ofconcentrically disposed tracks for data storage purposes, including userdata sectors and servo sectors. Each data storage disk 14 is mounted ona hub or spindle 16, which in turn is rotatably interconnected with abase plate 12 and/or cover. Multiple data storage disks 14 are typicallymounted in vertically spaced and parallel relation on the spindle 16. Aspindle motor 18 rotates the data storage disks 14 at an appropriaterate.

The disk drive 10 also includes an actuator arm assembly 24 that pivotsabout a pivot bearing 22, which in turn is rotatably supported by thebase plate 12 and/or cover. The actuator arm assembly 24 includes one ormore individual rigid actuator arms 26 that extend out from near thepivot bearing 22. Multiple actuator arms 26 are typically disposed invertically spaced relation, with one actuator arm 26 being provided foreach major data storage surface of each data storage disk 14 of the diskdrive 10. Other types of actuator arm assembly configurations may beutilized as well, such as an assembly having one or more rigid actuatorarm tips or the like that cantilever from a common structure. Movementof the actuator arm assembly 24 is provided by an actuator arm driveassembly, such as a voice coil motor 20 or the like. The voice coilmotor (VCM) 20 is a magnetic assembly that controls the operation of theactuator arm assembly 24 under the direction of control electronics 40.

A suspension 28 is attached to the free end of each actuator arm 26 andcantilevers therefrom. The slider 30 is disposed at or near the free endof each suspension 28. What is commonly referred to as the read/writehead (e.g., transducer) is mounted as a head unit 32 under the slider 30and is used in disk drive read/write operations. As the suspension 28moves, the slider 30 moves along arc path 34 and across thecorresponding data storage disk 14 to position the head unit 32 at aselected position on the data storage disk 14 for the disk driveread/write operations. When the disk drive 10 is not in operation, theactuator arm assembly 24 may be pivoted to a parked position utilizingramp assembly 42. The head unit 32 is connected to a preamplifier 36 viahead wires routed along the actuator arm 26, which is interconnectedwith the control electronics 40 of the disk drive 10 by a flex cable 38that is typically mounted on the actuator arm assembly 24. Signals areexchanged between the head unit 32 and its corresponding data storagedisk 14 for disk drive read/write operations.

The data storage disks 14 comprise a plurality of embedded servo sectorseach comprising coarse head position information, such as a trackaddress, and fine head position information, such as servo bursts. Asthe head 32 passes over each servo sector, a read/write channel (orservo control system) processes the read signal emanating from the headto demodulate the position information. The control circuitry processesthe position information to generate a control signal applied to the VCM20. The VCM 20 rotates the actuator arm 26 in order to position the headover a target track during the seek operation, and maintains the headover the target track during a tracking operation.

The head unit 32 may utilize various types of read sensor technologiessuch as anisotropic magnetoresistive (AMR), giant magnetoresistive(GMR), tunneling magnetoresistive (TMR), other magnetoresistivetechnologies, or other suitable technologies.

FIG. 2 shows a conventional disk format 200 including a number of servotracks 204 defined by servo sectors 206 ₀-206 _(N) recorded around thecircumference of each servo track. Each servo sector 206 _(i) includes apreamble 208 for storing a periodic pattern, which allows proper gainadjustment and timing synchronization of the read signal, and a syncmark 210 for storing a special pattern used to symbol synchronize to aservo data field 212. The servo data field 212 stores coarse headpositioning information, such as a servo track address, used to positionthe head over a target data track during a seek operation. Each servosector 206 _(i) further includes groups of servo bursts 214 (e.g., N andQ servo bursts), which are recorded with a predetermined phase relativeto one another and relative to the servo track centerlines. The phasebased servo bursts 214 provide fine head position information used forcenterline tracking while accessing a data track during write/readoperations. A position error signal (PES) is generated by reading theservo bursts 214, wherein the PES represents a measured position of thehead relative to a centerline of a target servo track. A servocontroller processes the PES to generate a control signal applied to ahead actuator (e.g., a voice coil motor) in order to actuate the headradially over the disk in a direction that reduces the PES.

Referring to FIG. 3, a portion of hard disk drive (HDD) is illustrated,according to an embodiment, including a head 316 and a disk 318. Thedisk 318 includes a plurality of servo tracks 320, wherein each servotrack includes a plurality of servo sectors 322 ₀-322 _(N). The diskdrive further includes control circuitry 324 including a servo controlsystem operable to actuate the head over the disk in response to theservo sectors 322 ₀-322 _(N). The disk is rotated by a spindle motor 346at a rotational speed that is controlled by the control circuitry 324,for example, a motor driver of the control circuitry 324.

Control circuitry 324 processes a read signal 332 emanating from thehead 316 to demodulate the servo sectors 322 ₀-322 _(N) and generate aposition error signal (PES) representing an error between the actualposition of the head and a target position relative to a target track.In an embodiment, the target track includes a target data track definedrelative to the servo tracks 320, wherein the data tracks may berecorded at the same or different radial density than the servo tracks320. The control circuitry 324 filters the PES using a suitablecompensation filter to generate a control signal 334 applied to a voicecoil motor (VCM) 336, which rotates an actuator arm 338 about a pivot inorder to actuate the head 316 radially over the disk 318 in a directionthat reduces the PES. The control circuitry 324 may also generate acontrol signal 340 applied to a microactuator 342 in order to actuatethe head 316 over the disk 318 in fine movements. Any suitablemicroactuator 342 may be employed in the embodiments, such as apiezoelectric actuator. In addition, the microactuator 342 may actuatethe head 316 over the disk 318 in any suitable manner, such as byactuating a suspension relative to the actuator arm, or actuating aslider relative to the suspension. The servo sectors 322 ₀-322 _(N) mayinclude any suitable head position information, such as a track addressfor coarse positioning and servo bursts for fine positioning. The servobursts may include any suitable pattern, such as an amplitude basedservo pattern or a phase based servo pattern.

To accomplish reading and writing of data to and from the disk, thecontrol circuitry may include a read channel configured to process theread signal 332 from the head 316 and a write channel to prepare writesignal 332 for sending to the head 316 for writing.

In an embodiment, head 316 is a TDMR head with multiple reader elements,allowing extraction of multiple read signals and subsequently improvedSNR gains via signal processing the signal from multiple readerelements. The reader elements read the same track or adjacent tracks. Inan embodiment, TDMR gains are provided when reading mostly the sametrack or processing signal from a main track and its adjacent tracks. Inan embodiment, head 316 is a TDMR head that may be used with tracksincluding spiral data tracks, as well as conventional concentric datatracks.

In an embodiment, there is a separation between the individual readerelements, which can vary greatly over process, for each head. For a TDMRdata or servo operation, the separation of the reader elements issituated for optimal digital signal processing (DSP) of the signals fromthe different reader elements. In an embodiment, the reader elementseparation is measured with high precision at different locations on thedisk (e.g., adjusting for different actuator positions). In anembodiment, the TDMR head increases the data density of the recordingmedia. In an embodiment, two reader elements, while accessing a targettrack, are separated and offset from a position centerline of the targettrack. In an embodiment, when the second reader element, but not thefirst reader element, is caused to read the magnetic storage medium,then the second reader element is repositioned to a position that iscenterline to a target track.

In an embodiment, the magnetic storage medium reader system includes atleast a first reader system and a second reader system. The first readersystem includes a first reader element, and the second reader systemincludes a second reader element. Head 316 includes the first readerelement and the second reader element. Control circuitry 324 isreconfigured during manufacturing of the magnetic storage medium readersystem to cause the second reader system, but not the first readersystem, to read a magnetic storage medium, when the first reader systemis determined during the manufacturing to provide less than apredetermined performance or to be nonfunctioning.

In an embodiment, the second reader system is utilized with anon-two-dimensional magnetic recording (TDMR) data storage device.

In an embodiment, when the first reader system is determined during themanufacturing to provide less than a predetermined performance or to benonfunctioning, the second reader system and a third reader system areutilized to read the magnetic storage medium. In this embodiment, thesecond reader system and the third reader system are utilized with atwo-dimensional magnetic recording (TDMR) data storage device.

In an embodiment, when the first reader system is determined during themanufacturing to provide less than a predetermined performance or to benonfunctioning, the magnetic storage medium reader system isreconfigured to i.) read at a track per inch (TPI) data density that isless than if the first reader system provided at least a predeterminedperformance and was additionally utilized, and/or ii.) provide a readsignal at a signal to noise ratio (SNR) that is less than if the firstreader system provided at least a predetermined performance and wasadditionally utilized.

In an embodiment, the second reader system includes a second readerelement and a second read channel. The second reader system isstructured such that when a second reader element signal is created, thesecond reader element signal travels from the second reader element tothe second read channel. The first reader system includes a first readerelement and a first read channel.

In an embodiment, when the second reader system is utilized to read themagnetic storage medium, the second reader system utilizes one portionor more than one portion of the second reader system to read themagnetic storage medium.

In an embodiment, when the first reader system is not utilized to readthe magnetic storage medium, one portion or more than one portion of thefirst reader system is not utilized.

In an embodiment, the waterfall method and process described herein mayinclude reconfiguring a reader system, changing servo operations, dataformatting, and/or firmware control. In an embodiment, various servocontrol and data channel values may be encoded in one or more lookuptables, so these values provide options to accommodate various waterfallscenarios. In an embodiment, the waterfall process includes employingvarious pre-defined versions of firmware that can be selected forinstallation to a final drive product, depending on whether a waterfallprocess is utilized.

FIG. 4 illustrates a waterfall method and process for manufacturing adata storage system, in an embodiment. Each step in the flowchartillustration can be implemented by computer program instructions, in anembodiment. These computer program instructions may be provided to aprocessor of a programmable data processing apparatus, such that theinstructions execute via the processor to implement the functions oractions specified in the flowchart. The instructions may be executed bya controller. In an embodiment, the controller is a component of a datastorage device, such as a disk drive storage system. In an alternativeembodiment, the controller is separate from the data storage device andmay be connected to the data storage device to externally monitor andcommunicate with the data storage device.

As detailed in step 402, it is determined during manufacturing of amagnetic storage medium reader system, including at least a first readersystem and a second reader system, whether the first reader systemprovides less than a predetermined performance or is nonfunctioning, inan embodiment. The first reader system includes a first reader element,and the second reader system includes a second reader element. A firsthead includes both the first reader element and the second readerelement.

Next, as stated in step 404, the magnetic storage medium reader systemis reconfigured during the manufacturing to utilize the second readersystem, but not utilize the first reader system, to read the magneticstorage medium, when the first reader system is determined during themanufacturing to provide less than the predetermined performance or isnonfunctioning.

In an embodiment, the second reader system is utilized with anon-two-dimensional magnetic recording (non-TDMR) data storage device,when the first reader system is determined to provide less than thepredetermined performance or is nonfunctioning.

In an embodiment, the manufacturing of the magnetic storage mediumreader system includes a reader system with a two-dimensional magneticrecording (TDMR) head. Following steps 402 and 404, the method furtherincludes utilizing the second reader system with a non-TDMR data storagedevice, rather than with the TDMR data storage device, when the firstreader system is determined to provide less than the predeterminedperformance or is nonfunctioning.

In an embodiment, following steps 402 and 404, the second reader systemis utilized with a non-TDMR data storage device, whether or not themanufacturing of the magnetic storage medium reader system included areader system with a TDMR head when the first reader system wasdetermined to provide less than a predetermined performance or wasnonfunctioning.

In an embodiment, following steps 402 and 404, the second reader systemis utilized with a TDMR data storage device, when the manufacturing ofthe magnetic storage medium reader system included a reader system witha TDMR head, and when a third, a fourth or additional reader systemsprovide at least a predetermined performance.

In an embodiment, following steps 402 and 404, when the magnetic storagemedium reader system further includes a third reader system, the secondreader system and the third reader system are utilized with atwo-dimensional magnetic recording (TDMR) data storage device.

In an embodiment, following step 402, when the magnetic storage mediumreader system further includes a third reader system, a fourth readersystem, or more than four reader systems, the magnetic storage mediumreader system is reconfigured during manufacturing to utilize readersystems that are providing at least a predetermined performance (e.g.,second reader system, third reader system, and fourth reader system). Inan embodiment, following step 402, the magnetic storage medium readersystem is reconfigured during manufacturing to utilize any number ofreader systems or reader heads that are providing at least apredetermined performance.

In an embodiment, following steps 402 and 404, the magnetic storagemedium reader system is reconfigured to at least read at a track perinch (TPI) data density that is less than if the first reader systemprovided at least the predetermined performance and was additionallyutilized, and/or provide a read signal at a signal to noise ratio (SNR)that is less than if the first reader system provided at least thepredetermined performance and was additionally utilized.

In an embodiment, the second reader system includes the second readerelement and a second read channel. The second reader system isstructured such that when a second reader element signal is created, thesecond reader element signal travels from the second reader element tothe second read channel. The first reader system includes the firstreader element and a first read channel.

In an embodiment, when the second reader system is utilized to read themagnetic storage medium, one portion or more than one portion of thesecond reader system is utilized to read the magnetic storage medium.

In an embodiment, when the first reader system is not utilized to readthe magnetic storage medium, one portion or more than one portion of thefirst reader system is not utilized.

In an embodiment, when the first reader system is not utilized, at leastone component of the first reader system is utilized with the magneticstorage medium reader system, but a signal from the first reader systemis not utilized.

In an embodiment, it is determined during manufacturing of the magneticstorage medium reader system whether a third reader system provides lessthan a predetermined performance or is nonfunctioning. The third readersystem includes a third reader element. The first head further includesthe third reader element. Next, the magnetic storage medium readersystem is reconfigured during the manufacturing to utilize the secondreader system, but not utilize the third reader system, to read themagnetic storage medium, when the third reader system is determinedduring the manufacturing to provide less than a predeterminedperformance or is nonfunctioning.

In an embodiment, before there is a determination that the first readersystem provides less than a predetermined performance or isnonfunctioning, the first reader system and the second reader system areutilized together to read the magnetic storage medium. In an alternativeembodiment, the second reader system is only employed in lieu of thefirst reader system, when the first reader system is determined toprovide less than a predetermined performance or is nonfunctioning.

In an embodiment, reconfiguring the reader system during manufacturingincludes directing or redirecting components of a TDMR drive such asservo, data channel, and controller firmware in the event that a readersystem provides less than a predetermined performance or isnonfunctioning. For example, a data storage device firmware may have acontingency code that is activated upon determination of a reader systemfailure during manufacturing. In an embodiment, pre-defined normal andfailure mode parameters/configuration values (e.g. related to channel,servo, etc.) may be stored in a lookup table (e.g., stored innon-volatile memory). In an embodiment, the memory may also be a diskmedia, with parameters read off of the reserve tracks at drive power upand stored in the system DDR buffer memory during operation of the harddrive. If failure mode is initiated, the appropriate table values areused. Once the failover method is employed, the properly performingreader element(s) are employed. In an embodiment, if a reader system isdetermined to provide less than a predetermined performance duringmanufacturing, it may be used for a limited purpose.

FIG. 5 is a flow diagram illustrating an alternative waterfall methodfor a data storage system, in an embodiment. As detailed in step 502, itis determined during manufacturing of a magnetic storage medium readersystem, including at least a first reader system and a second readersystem, whether the first reader system provides less than apredetermined performance, in an embodiment. The first reader systemincludes a first reader element, and the second reader system includes asecond reader element. A first head includes both the first readerelement and the second reader element. Next, as detailed in step 504,the first reader system is retained when the first reader system isdetermined to provide less than the predetermined performance. Asdetailed in step 506, the magnetic storage medium reader system isreconfigured to read the magnetic storage medium at less than thepredetermined performance, or the magnetic storage medium reader systemis situated with an alternative data storage device configured tofunction with less than the predetermined performance.

In an embodiment, the first reader system and the second reader systemare situated with a non-two-dimensional magnetic recording (TDMR) datastorage device, when the first reader system is determined to provideless than the predetermined performance.

In an embodiment, the magnetic storage medium reader system ismanufactured with a two-dimensional magnetic recording (TDMR) head.Following steps 502, 504 and 506, in an embodiment, the method furtherincludes situating the first reader system and the second reader systemwith a non-TDMR data storage device, rather than with the TDMR datastorage device, when the first reader system is determined to provideless than the predetermined performance.

In an embodiment, the magnetic storage medium reader system furtherincludes a third reader system, and the first reader system, the secondreader system, and a third reader system are situated with atwo-dimensional magnetic recording (TDMR) data storage device.

In an embodiment, following steps 502, 504 and 506, the magnetic storagemedium reader system is reconfigured to read at a track per inch (TPI)data density that is less than if the first reader system provided atleast the predetermined performance, and/or provide a read signal at asignal to noise ratio (SNR) that is less than if the first reader systemprovided at least the predetermined performance.

In an embodiment, inputs from two reader elements on one head areutilized in a reader array. In an alternative embodiment, more than tworeader elements on one head may be utilized to read a magnetic storagemedium, and signals from multiple reader elements may input to a readchannel and control circuitry.

Any suitable control circuitry may be employed to implement the methodsdescribed herein, such as any suitable integrated circuit or circuits.For example, control circuitry may be implemented within a read channelintegrated circuit, or in a component separate from the read channel,such as a disk controller, or certain operations described herein may beperformed by a read channel and others by a disk controller. In anembodiment, the read channel and disk controller are implemented asseparate integrated circuits, and in an alternative embodiment they arefabricated into a single integrated circuit or system on a chip (SOC).In addition, the control circuitry may include a suitable preamp circuitimplemented as a separate integrated circuit, integrated into the readchannel or disk controller circuit, or integrated into a SOC. Inembodiment, the control circuitry includes suitable logic circuitry,such as state machine circuitry.

In an embodiment, the control circuitry or DSP includes a microprocessorexecuting instructions, the instructions being operable to cause themicroprocessor to perform the methods described herein. The instructionsmay be stored in any computer-readable medium. In an embodiment, theymay be stored on a non-volatile semiconductor memory external to themicroprocessor, or integrated with the microprocessor in a SOC. Inanother embodiment, the instructions are stored on the disk and readinto a volatile semiconductor memory when the disk drive is powered on.

In an embodiment, control circuitry detects when a first reader systemprovides less than a predetermined performance or is nonfunctioning, andthereafter causes a second reader system, but not the first readersystem, to read the magnetic storage medium. In an embodiment, thecontrol circuitry includes a controller and/or firmware. In anembodiment, one or more reader quality metrics (e.g., SNR of a signal)are detected by the control circuitry. In an embodiment, in-linecalibrations may detect that a read element provides less than apredetermined performance or is nonfunctioning, despite failed sectorsnot being detected.

In an embodiment, when a first reader system and a second reader systemare both determined to provide less than a predetermined performance,then control circuitry determines which reader system provides thebetter quality signal, and the reader system providing the betterquality signal is utilized to read the magnetic storage medium.

In an embodiment, multiple reader element signals on one head input toone read channel. In an alternative embodiment, multiple reader elementsignals input to separate read channels. In yet another embodiment,multiple reader element signal pathways utilize portions of the sameread channel, as well as utilize separate circuitry.

In an embodiment, when there is a determination that a first readersystem provides less than a predetermined performance or isnonfunctioning, all of, or a portion of, the first reader system is notutilized to read the magnetic storage medium. For example, when only oneportion of the first reader system is nonfunctioning (e.g., first readersystem analog-to-digital converter), the first reader system maycontinue to use the functioning portion of first reader system, andalternatively use a portion of a second reader system (e.g., secondreader system analog-to-digital converter) to read the magnetic storagemedium.

Similarly, in an embodiment, when the second reader system is caused toread the magnetic storage medium, the second reader system may utilizeone portion or more than one portion of the second reader system to readthe magnetic storage medium.

In an embodiment, a third reader element is included with a head thatincludes a first reader element and a second reader element. When thereis a determination that a first reader system and a third reader systemprovide less than a predetermined performance or is nonfunctioning, thesecond reader system, but not the first reader system or the thirdreader element (including, e.g., a third reader system) is caused toread the magnetic storage medium.

Turning now to FIG. 6, components of system 600 are illustrated, in anembodiment. System 600 includes processor module 604, storage module606, input/output (I/O) module 608, memory module 610, and bus 602.Although system 600 is illustrated with these modules, other suitablearrangements (e.g., having more or less modules) known to those ofordinary skill in the art may be used. For example, system 600 may be alogic implemented state machine or a programmable logic controller.

In an embodiment, the methods described herein are executed by system600. Specifically, processor module 604 executes one or more sequencesof instructions contained in memory module 610 and/or storage module606. In one example, instructions may be read into memory module 610from another machine-readable medium, such as storage module 606. Inanother example, instructions may be read directly into memory module610 from I/O module 608, for example from an operator via a userinterface. Information may be communicated from processor module 604 tomemory module 610 and/or storage module 606 via bus 602 for storage. Inan example, the information may be communicated from processor module604, memory module 610, and/or storage module 606 to I/O module 608 viabus 602. The information may then be communicated from I/O module 608 toan operator via the user interface.

Memory module 610 may be random access memory or other dynamic storagedevice for storing information and instructions to be executed byprocessor module 604. In an example, memory module 610 and storagemodule 606 are both a machine-readable medium.

In an embodiment, processor module 604 includes one or more processorsin a multi-processing arrangement, where each processor may performdifferent functions or execute different instructions and/or processescontained in memory module 610 and/or storage module 606. For example,one or more processors may execute instructions for determining readelement performance during the manufacturing of a magnetic storagemedium reader system, and one or more processors may executeinstructions for input/output functions. Also, hard-wired circuitry maybe used in place of or in combination with software instructions toimplement various example embodiments. Thus, embodiments are not limitedto any specific combination of hardware circuitry and software.

The term “circuit” or “circuitry” as used herein includes all levels ofavailable integration, for example, from discrete logic circuits to thehighest level of circuit integration such as VLSI, and includesprogrammable logic components programmed to perform the functions ofembodiments as well as general-purpose or special-purpose processorsprogrammed with instructions to perform those functions.

Bus 602 may be any suitable communication mechanism for communicatinginformation. Processor module 604, storage module 606, I/O module 608,and memory module 610 are coupled with bus 602 for communicatinginformation between any of the modules of system 600 and/or informationbetween any module of system 600 and a device external to system 600.For example, information communicated between any of the modules ofsystem 600 may include instructions and/or data.

The term “machine-readable medium” as used herein, refers to any mediumthat participates in providing instructions to processor module 604 forexecution. Such a medium may take many forms, including, but not limitedto, non-volatile media, and volatile media. Non-volatile media includes,for example, optical or magnetic disks, such as storage module 606.Volatile media includes dynamic memory, such as memory module 610.Common forms of machine-readable media or computer-readable mediainclude, for example, floppy disk, a flexible disk, hard disk, magnetictape, any other magnetic medium, a CD-ROM, DVD, any other opticalmedium, punch cards, paper tape, any other physical mediums withpatterns of holes, a RAM, a PROM, an EPROM, a FLASH EPROM, any othermemory chip or cartridge, or any other medium from which a processor canread.

In an embodiment, a non-transitory machine-readable medium is employedincluding executable instructions for a data storage device. Theinstructions include code for determining during manufacturing of amagnetic storage medium reader system, including at least a first readersystem and a second reader system, whether the first reader systemprovides less than a predetermined performance or is nonfunctioning. Thefirst reader system includes a first reader element, and the secondreader system includes a second reader element. A first head includesboth the first reader element and the second reader element. Theinstructions further include code for reconfiguring the magnetic storagemedium reader system during the manufacturing to utilize the secondreader system, but not utilize the first reader system, to read themagnetic storage medium, when the first reader system is determinedduring the manufacturing to provide less than the predeterminedperformance or is nonfunctioning.

In an embodiment, the non-transitory machine-readable medium furtherincludes executable instructions for determining during manufacturing ofa magnetic storage medium reader system, including at least a firstreader system and a second reader system, whether the first readersystem provides less than a predetermined performance. The first readersystem includes a first reader element, and the second reader systemincludes a second reader element. A first head includes both the firstreader element and the second reader element.

The instructions further include code for retaining the first readersystem when the first reader system is determined to provide less than apredetermined performance.

The instructions further include code for reconfiguring the magneticstorage medium reader system to read the magnetic storage medium at theless than the predetermined performance, or situating the magneticstorage medium reader system with an alternative data storage deviceconfigured to function with less than the predetermined performance.

The various features and processes described herein may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure. In addition, certain method, event orprocess blocks may be omitted in some implementations. The methods andprocesses described herein are also not limited to any particularsequence, and the blocks or states relating thereto can be performed inother sequences that are appropriate. For example, described tasks orevents may be performed in an order other than that specificallydisclosed, or multiple may be combined in a single block or state. Theexample tasks or events may be performed in serial, in parallel, or insome other manner. Tasks or events may be added to or removed from thedisclosed example embodiments. The example systems and componentsdescribed herein may be configured differently than described. Forexample, elements may be added to, removed from, or rearranged comparedto the disclosed example embodiments.

While certain example embodiments have been described, these embodimentshave been presented by way of example only, and are not intended tolimit the scope of the embodiments disclosed herein. Thus, nothing inthe foregoing description is intended to imply that any particularfeature, characteristic, step, module, or block is necessary orindispensable. Indeed, the novel methods and systems described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the embodiments disclosed herein.

Modifications and variations may be made to the disclosed embodimentswhile remaining within the spirit and scope of the methods, systems andapparatus. The implementations described above and other implementationsare within the scope of the following claims.

We claim:
 1. A magnetic storage medium reader system for a data storagedevice, comprising: at least a first reader system and a second readersystem, the first reader system including a first reader element, andthe second reader system including a second reader element; a first headincluding the first reader element and the second reader element; andcontrol circuitry reconfigured during manufacturing of the magneticstorage medium reader system to cause the second reader system, but notthe first reader system, to read a magnetic storage medium, the firstreader system determined during the manufacturing to provide less than apredetermined performance or to be nonfunctioning.
 2. The magneticstorage medium reader system of claim 1, wherein the second readersystem is utilized with a non-two-dimensional magnetic recording (TDMR)data storage device.
 3. The magnetic storage medium reader system ofclaim 1, further comprising a third reader system to read the magneticstorage medium, wherein the second reader system and the third readersystem are utilized with a two-dimensional magnetic recording (TDMR)data storage device.
 4. The magnetic storage medium reader system ofclaim 1, wherein the magnetic storage medium reader system isreconfigured to at least one of: read at a track per inch (TPI) datadensity that is less than if the first reader system provided at leastthe predetermined performance and was additionally utilized, and providea read signal at a signal to noise ratio (SNR) that is less than if thefirst reader system provided at least the predetermined performance andwas additionally utilized.
 5. The magnetic storage medium reader systemof claim 1, wherein: utilizing the second reader system to read themagnetic storage medium comprises utilizing one portion or more than oneportion of the second reader system to read the magnetic storage medium;and not utilizing the first reader system to read the magnetic storagemedium comprises not utilizing one portion or more than one portion ofthe first reader system.
 6. A method for manufacturing a data storagedevice, comprising: determining during manufacturing of a magneticstorage medium reader system, including at least a first reader systemand a second reader system, whether the first reader system providesless than a predetermined performance or is nonfunctioning, wherein thefirst reader system includes a first reader element, and the secondreader system includes a second reader element, and wherein a first headincludes both the first reader element and the second reader element;and reconfiguring the magnetic storage medium reader system during themanufacturing to utilize the second reader system, but not utilize thefirst reader system, to read the magnetic storage medium, when the firstreader system is determined during the manufacturing to provide the lessthan the predetermined performance or is nonfunctioning.
 7. The methodof claim 6, wherein the manufacturing is manufacturing of a magneticstorage medium reader system that includes a two-dimensional magneticrecording (TDMR) head, the method further comprising utilizing thesecond reader system with a non-TDMR data storage device, rather thanwith the TDMR data storage device, when the first reader system isdetermined to provide the less than the predetermined performance or isnonfunctioning.
 8. The method of claim 6, further comprising utilizingthe second reader system with a non-two-dimensional magnetic recording(TDMR) data storage device, when the first reader system is determinedto provide the less than the predetermined performance or isnonfunctioning.
 9. The method of claim 6, further comprising utilizingthe second reader system and a third reader system with atwo-dimensional magnetic recording (TDMR) data storage device, whereinthe magnetic storage medium reader system further includes the thirdreader system.
 10. The method of claim 6, further comprisingreconfiguring the magnetic storage medium reader system to at least oneof: read at a track per inch (TPI) data density that is less than if thefirst reader system provided at least the predetermined performance andwas additionally utilized, and provide a read signal at a signal tonoise ratio (SNR) that is less than if the first reader system providedat least the predetermined performance and was additionally utilized.11. The method of claim 6, wherein the second reader system includes thesecond reader element and a second read channel, the second readersystem structured such that when a second reader element signal iscreated, the second reader element signal travels from the second readerelement to the second read channel; and wherein the first reader systemincludes the first reader element and a first read channel.
 12. Themethod of claim 6, wherein: utilizing the second reader system to readthe magnetic storage medium comprises utilizing one portion or more thanone portion of the second reader system to read the magnetic storagemedium; and not utilizing the first reader system to read the magneticstorage medium comprises not utilizing one portion or more than oneportion of the first reader system.
 13. The method of claim 6, whereinnot utilizing the first reader system comprises including at least onecomponent of the first reader system with the magnetic storage mediumreader system, but not utilizing a signal from the first reader system.14. The method of claim 6, further comprising: determining during themanufacturing of the magnetic storage medium reader system whether athird reader system provides less than the predetermined performance oris nonfunctioning, wherein the third reader system includes a thirdreader element, and wherein the first head further includes the thirdreader element; and reconfiguring the magnetic storage medium readersystem during the manufacturing to utilize the second reader system, butnot utilize the third reader system, to read the magnetic storagemedium, when the third reader system is determined during themanufacturing to provide the less than the predetermined performance oris nonfunctioning.
 15. The method of claim 6, wherein reconfiguring themagnetic storage medium reader system during the manufacturing toutilize the second reader system comprises configuring the second readerelement to reposition, during reading of a target track, from offset ofthe centerline of the target track to centerline of the target track.16. A method for a data storage device, comprising: determining duringmanufacturing of a magnetic storage medium reader system, including atleast a first reader system and a second reader system, whether thefirst reader system provides less than a predetermined performance,wherein the first reader system includes a first reader element, and thesecond reader system includes a second reader element, and wherein afirst head includes both the first reader element and the second readerelement; retaining the first reader system when the first reader systemis determined to provide the less than the predetermined performance;and reconfiguring the magnetic storage medium reader system to read themagnetic storage medium at the less than the predetermined performance,or situating the magnetic storage medium reader system with analternative data storage device configured to function with the lessthan the predetermined performance.
 17. The method of claim 16, whereinthe manufacturing is manufacturing of a magnetic storage medium readersystem that includes a two-dimensional magnetic recording (TDMR) head,the method further comprising situating the first reader system and thesecond reader system with a non-TDMR data storage device, rather thanwith the TDMR data storage device, when the first reader system isdetermined to provide the less than the predetermined performance. 18.The method of claim 16, further comprising situating the first readersystem and the second reader system with a non-two-dimensional magneticrecording (TDMR) data storage device, when the first reader system isdetermined to provide the less than the predetermined performance. 19.The method of claim 16, further comprising situating the first readersystem, the second reader system, and a third reader system with atwo-dimensional magnetic recording (TDMR) data storage device, whereinthe magnetic storage medium reader system further includes the thirdreader system.
 20. The method of claim 16, further comprisingreconfiguring the magnetic storage medium reader system to at least oneof: read at a track per inch (TPI) data density that is less than if thefirst reader system provided at least the predetermined performance, andprovide a read signal at a signal to noise ratio (SNR) that is less thanif the first reader system provided at least the predeterminedperformance.